This invention relates to an apparatus for supplying a liquid to a heated surface, and particulaly, but not exclusively, to the application of release oil in the heated fuser roll of a xerographic copying machine.
In a typical plain paper zerographic copying machine, a fuser is used to permanently fix a toner image to a copy sheet. The toner consists of coloured resinous particles which, on the application of heat and pressure, become permanently bonded to the paper so as to resemble conventional printing. One problem which arises with fusers of the heated roller type is that the toner tends to adhere to the heated roller, with the result that dirty copies may then be made due to transfer of unwanted toner from the fuser roller to subsequent copy sheets. In order to prevent this, a release oil is applied to the heated fuser roller, so that none of the toner adheres to the heated roller.
In known release oil applicators for heated roller fuses, a wick is used to apply the release oil. Although generally satisfactory, capillary supply to such a wick has given rise to problems when the oil used is of relatively high viscosity. One way of solving the problem is to slowly but positively pump the release oil along a manifold which supplies oil to the applicator wick at a series of supply ports spaced along the roller. Once again a problem arises in that the oil in the manifold becomes heated by heat from the roller so that when the fuser is inoperative, and cools to room temperature, the oil contracts with the result that it tends to draw air bubbles through the supply ports and into the manifold. These air bubbles then tend to coalesce and redistribute themselves within the manifold, and may make it impossible for oil to be supplied through some of the ports, giving rise to dry spots along the wick.